Cell multiplexing apparatus handling multiple items of information

ABSTRACT

A cell multiplexing apparatus including call monitors and multiplexers. The call monitors monitor a plurality of channels for their call setting status and select at least two channels for which the same cell may be assembled, i.e., for which the destination of the calls is the same. The multiplexers receive audio information or information already assembled in asynchronous transfer mode (ATM) cells from the channels selected by the call monitors, and disassemble and multiplex the received information for assembly into the payload of a new ATM cell.

BACKGROUND OF THE INVENTION

The present invention relates to an asynchronous transfer mode (ATM)transmission apparatus for multiplexing coded audio signals into a cellfor transmission over a transmission network in an ATM mode.

Research is progressing on the so-called ISDN (integrated servicesdigital network). This is a branch of technologies for concurrentlytransmitting over a single network multiple pieces of information thathave different characteristics, such as audio information and dynamicimage information. Drawing attention in this area presently isasynchronous transfer mode (ATM), a switching technique indispensablefor implementing a broadened ISDN (B-ISDN). This technique involvesdividing communication information into packets called cells of a fixedlength for transmission.

The most commonly utilized method today for coding telephone voicesignals in digital format is pulse code modulation (PCM) at atransmission rate of 64 kilobits per second. Where it is desired tolower the transmission rate (also known as the bit rate) withoutdegrading the quality of voice transmitted, one known method employed isADPCM (adaptive differential pulse code modulation) at a transmissionrate of 32 kilobits per second.

About to be put into practice is what is known as low delay code excitedlinear prediction (LD-CELP:CCITT G728). This is a method for convertingevery five values sampled at 8 kHz into a predetermined code of 10 bits,whereby a transmission rate of 16 kilobits per second is provided.

Where voice signals are transmitted as communication information, thequality of voice sound deteriorates if the transmission delay timeinvolved is prolonged. Thus there are strict limits as to how long thetransmission delay time is allowed to be.

Described below is a typical setup of the abovementioned ATMtransmission using voice signals. FIG. 2 is a block diagram of a typicalprior art ATM transmission apparatus, and FIG. 3 is a view showing theconstitution of an ATM cell used by the conventional apparatus of FIG.2. In FIG. 2, an exchange 1 accommodates subscriber lines from aplurality of subscriber terminals 2 and is connected to the ATMtransmission apparatus 4 via a plurality of channels 5.

Suppose that one of the subscriber terminals 2 (i.e., callingsubscriber) makes a call to communicate with another subscriber terminal(i.e., called subscriber) via an ATM transmission line 3. In that case,the exchange 1 first connects the terminal 2 of the calling subscriberto the ATM transmission apparatus 4 over a given channel 5.

In turn, the ATM transmission apparatus 4 converts into a predetermineddigital code (called coded information) the voice signal transmittedfrom the subscriber terminal 2 (calling subscriber) through the exchange1 and channel 5. The ATM transmission apparatus 4 then generates an ATMcell 10, multiplexes it with another cell made of the voice signal fromthe subscriber terminal 2, and transmits the multiplexed result over theATM transmission line 3.

As depicted in FIG. 3, cells generated by the ATM transmission apparatus4 are each composed of 53 octets. The first five octets constitute anATM header 7. The ATM header 7 includes a virtual path identifier (VPI)and a virtual channel identifier (VCI). The remaining 48 octets make upa payload 8 comprising coded information.

Of the 48 octets constituting the payload, the first octet contains asequence number identifier (SN) and a data type identifier (IT) the lasttwo octets make up an effective data length identifier (LI) and a cyclicredundancy check identifier (CRC). The remaining 45 octets (i.e., 360bits) constitute a payload user information part 11 for transmitting thecoded information.

The ATM transmission apparatus 4 of FIG. 2 is equipped for each channel5 with a coder-decoder 41, a code buffer 42, a payload assembler 43 andan ATM multiplexer 13. The channels 5 are provided commonly with a crossconnection multiplexer 45. These components work as follows:

The coder-decoder 41 digitizes a voice signal illustratively accordingto the LD-CELP method. The voice signal has been transmitted from asubscriber terminal 2 (calling subscriber) over a channel 5 and throughthe exchange 1. The signal in digital format is stored in the codebuffer 42 downstream.

The payload assembler 43 monitors the amount of coded information in thecode buffer 42. On detecting an accumulation of 36 items of codedinformation (i.e., 360 bits, or 45 octets) in the code buffer 42, thepayload assembler 43 gets the accumulated 36 items of coded informationfrom the code buffer 42 and assembles them into a payload 8. The payload8 is then transferred to the ATM multiplexer 13 downstream.

Upon receipt of the payload 8 from the payload assembler 43, the ATMmultiplexer 13 composes a cell by adding an ATM header 7 to the payloadcoming from the payload assembler 43. The cell when composed istransferred to the cross connection multiplexer 45.

The cross connection multiplexer 45 stores temporarily in a queue (i.e.,buffer) the cells transferred from the ATM multiplexers 13 upstream. Thecells are then output onto the ATM transmission line 3 in the order inwhich they were stored into the buffer.

As described, in the prior art ATM transmission apparatus 4, the codedinformation made of the voice signals coming from subscriber terminals 2is transmitted over the ATM transmission line 3 after 36 items of thecoded information are accumulated in the code buffer 42 and areassembled into a cell for transmission.

It takes 625 microseconds (μs) for the coder-decoder 41 to generate oneitem of coded information (i.e., 125 μd×5). That is, a delay time of22,500 μs occurs by the time 36 items of coded information areaccumulated in the code buffer 42 (i.e., 625 μs×36). This often makes itdifficult to comply with the time constraints on transmission delayunder the LD-CELP method. As a result, a serious adverse effect on thequality of the transmitted voice may occur.

Presently, there is a possibility that in-house LAN's (local areanetworks), based on the DQDB (distributed queue dual bus) systemproposed under IEEE (Institute of Electrical and Electronics Engineers)802.6, will gain widespread acceptance. If that happens, the congestionof different types of communication information, which will effect upontransmission, can be a severe disadvantage to the system.

Packet data transmitted over the LAN's have variable lengths while ATMcells 10 have a fixed length. When communication information is divided,the divided items are multiplexed into an ATM cell 10. If a fraction ofthe cell 10 constitutes the information, the remaining vacant parts arefilled with dummy patterns so that the finished cell will be a completecell. The smaller the fraction and the higher the frequency at which afractionally complete cell occurs, the more dummy patterns are needed tofill the gap. As a result, the transmission efficiency decreases.

More and more terminals connected to in-house LAN's including those incompliance with the DQDB system will likely be multi-media terminalssuch as TV telephone sets and audio/visual output devices. There islittle doubt that the number of available channels will not keep up withthe growing number of multi-media terminals. Furthermore, if equippedwith a transmitter-receiver for each different medium, the multi-mediaterminal will bloat in size and cost and will run counter to today'strend toward downsized terminals with compact functions.

Certain kinds of communication information such as motion picturesrequire synchronism between dynamic image information and audioinformation when transmitted. Ensuring synchronism between the differentkinds of information is necessary so as to keep the received informationmeaningful. It may be arranged technically that each cell compriseseither audio or image information alone. In that case, a relativelysmall amount of audio information is in disproportionate contrast withlarge quantities of dynamic image information. This can result in whatis known as image cell drop-out, i.e., the rate of dynamic imageinformation transmission failing to keep up with the rate of audioinformation transmission. The image cell drop-out can be a major causeof deterioration in image quality.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a cellmultiplexing apparatus operating in asynchronous transfer mode (ATM),the apparatus minimizing the delay time required to transmitcommunication information of a single or a plurality of kinds over anATM transmission network while collectively handling communicationinformation of different media with no data drop-out.

In carrying out the invention and according to one aspect thereof, thereis provided a cell multiplexing apparatus which receives communicationinformation over at least two channels of any one of the same anddifferent kinds, and assembles the received information into anasynchronous transfer mode cell made of a fixed-length header and apayload, and which transmits the assembled cell. The apparatus comprisescall monitoring means for obtaining call setting information fromindividual items of the communication information and multiplexing meansfor multiplexing the communication information received over the minimumof two channels into a single asynchronous transfer mode cell of a fixedlength in accordance with the call setting information obtained by thecall monitoring means. In a preferred structure according to theinvention, the multiplexing means 200 may multiplex control and alarminformation from the channels 5 selected by the call monitoring meanstogether with, say, audio information into a cell. Alternatively, themultiplexing means 200 may assemble a cell using audio signals obtainedby converting a plurality of sampled values into a code of apredetermined number of bits. Because the communication information 6from the multiple channels 5 is multiplexed, as described, into a singlecell according to the invention, the transfer delay is minimized.

When a plurality of items information are multiplexed into a singlecell, the payload part of the cell may be formed to a fixed or variablelength. How the payload part is formed may be expressed as payloadcontrol information that is prefixed to the beginning of the payload 8.

The same kind of communication information (e.g., audio information) maybe multiplexed into a single cell. Alternatively, communicationinformation of different characteristics (audio and image information)may be multiplexed into a single cell.

In a further preferred structure according to the invention, a pluralityof ATM cells 10 received as communication information 6 may be dividedand the divided parts may be multiplexed into a new ATM cell 10.

These and other objects, features and advantages of the invention willbecome more apparent upon a reading of the following description andappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating the operating principle of the presentinvention;

FIG. 2 is a block diagram of a typical prior art ATM transmissionapparatus;

FIG. 3 is a view showing the constitution of an ATM cell used by theconventional apparatus of FIG. 2;

FIG. 4 is a block diagram depicting the overall system configuration ofa first embodiment of the invention;

FIG. 5 is a block diagram of an ATM transmission apparatus in the firstembodiment;

FIG. 6 is a view showing the format of an ATM cell used by the firstembodiment;

FIG. 7 is a conceptual view indicating how data items are multiplexed bythe first embodiment;

FIG. 8 is a detailed view showing how call monitors are illustrativelystructured in the first embodiment;

FIG. 9 is a view depicting typical sequences of control operations ineffect when a call is connected by the first embodiment;

FIG. 10 is a view portraying the sequence of operations between a codebuffer controller and a code buffer on the calling side where a call isconnected by the first embodiment;

FIG. 11 is a view showing the sequence of operations between a codebuffer controller and an ATM multiplexer on the called part where a callis connected by the first embodiment;

FIG. 12 is a view depicting the sequence of operations between a codebuffer controller and a code buffer on the called side where a call isconnected by the first embodiment;

FIG. 13 is a view illustrating the overall system configuration of asecond embodiment of the invention;

FIG. 14 is a function block diagram of a cell mapping part in the secondembodiment;

FIG. 15 is a conceptual view showing how ATM cells are multiplexed bythe second embodiment;

FIG. 16 is a view depicting the format of a channel identifier in a newATM cell produced by the second embodiment;

FIG. 17 is a block diagram portraying the overall system configurationof a third embodiment of the invention;

FIG. 18 is a view illustrating the format of a channel ID part in a newATM cell produced by the third embodiment;

FIG. 19 is a block diagram depicting the overall system configuration ofa fourth embodiment of the invention;

FIG. 20 is a conceptual view showing how ATM cells are multiplexed bythe fourth embodiment;

FIG. 21 is a block diagram sketching the overall system configuration ofa fifth embodiment of the invention;

FIG. 22 is a block diagram of an interface part that handles thetransmission and reception of ATM cells in the fifth embodiment;

FIG. 23 is a function block diagram showing how a buffer controller andan ATM multiplexer operate on the transmitting side of the fifthembodiment;

FIG. 24 is a function block diagram depicting how a buffer controllerand an ATM multiplexer operate on the receiving side of the fifthembodiment;

FIG. 25 is a conceptual view illustrating how ATM cells are multiplexedby the fifth embodiment;

FIG. 26 is a view showing typical contents of payload controlinformation parts in ATM cells in connection with the fifth embodiment;

FIG. 27 is a view describing how the ATM cells multiplexed by the fifthembodiment as shown in FIG. 25 are restored back to the originalinformation;

FIG. 28 is a view showing a detailed format of an ATM cell in connectionwith the fifth embodiment;

FIG. 29 is a view indicating what is typically meant by a DB headerstored in a payload control information part in connection with thefifth embodiment;

FIG. 30 is a view depicting typical contents of a DC header stored in apayload control information part in connection with the fifthembodiment; and

FIG. 31 is a view showing the format of an ATM cell that actuallycontains information in connection with the fifth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In FIG. 1, call monitoring means 100 monitors each of the multiplechannels 5 for the call setting status in order to select a plurality ofchannels 5 for which the same cell may be assembled (i.e., for the samedestination). Cell multiplexing means 200 takes audio information or ATMcells from the multiple channels 5 selected by the call monitoring means100, divides the received information or ATM cells, and assembles thedivided parts in a multiplexing manner into a new cell (containing apayload 8).

The first embodiment of the invention is arranged to divide audioinformation from a plurality of channels into ATM cells 10 of a fixedlength each for multiplexing. FIG. 4 depicts the overall systemconfiguration of the first embodiment, FIG. 5 is a block diagram of anATM transmission apparatus in the first embodiment, and FIG. 6 shows theformat of an ATM cell used by the first embodiment.

FIG. 7 is a conceptual view indicating how data items are multiplexed bythe first embodiment. FIG. 7 shows how audio information from aplurality of channels 5 (data A, data B, data C, . . . ) is multiplexedinto ATM cells 10.

In FIG. 4, an exchange 1 accommodating subscriber lines from subscriberterminals 2 is connected to an ATM transmission apparatus 4. The ATMtransmission apparatus 4 on the calling side is in turn connected via anATM transmission line 3 to another ATM transmission apparatus 4 on thecalled side.

In FIG. 5, call monitors 46 constituting call monitoring means 10 areprovided in the ATM transmission apparatus 4. The call monitors 46 arerespectively connected to ATM processors 44. Each ATM processor 44comprises coder-decoders 41, a data multiplexer 36 and an ATMmultiplexer 13, the latter two constituting multiplexing means 200.

Referring again to FIG. 4, suppose that a subscriber (callingsubscriber) wishes to make a call to another subscriber (calledsubscriber). In that case, the exchange 1 connects the callingsubscriber's terminal 2 to the ATM transmission apparatus 4 via a givenchannel 5. In FIG. 5, the calling subscriber sends to the ATMtransmission apparatus 4 call setting information for setting up thecall.

In the ATM transmission apparatus 4, the call monitors 46 monitors thecall setting information coming from the calling subscribers over thechannels (data A-n). From the call setting information, each callmonitor 46 obtains the settings needed to determine a virtual pathidentifier VPI and a virtual channel identifier VCI for the relevant ATMprocessor 44. The settings are transferred along with identificationinformation of each channel 5 to the data multiplexer 36. The transferis made to a buffer controller 12 (buffer control means 12) in the datamultiplexer 36 via a control line 37 provided independently of the datacommunication lines.

How each call monitor is typically structured will now be described withreference to FIG. 8. As shown in FIG. 8, each call monitor comprisescall monitor units 38 provided for the respective channels, a controlsignal transmitter-receiver 15 for recognizing a channel control signalreceived over the channels 5, and a transmission path selector 16 forobtaining path information from the channel control signal.

The control information including the channel control information may beobtained on an in-slot basis (i.e., the information is contained in theaudio signal from the channels 5), or on an out-slot basis (theinformation is received over a separate control line 37 independent ofthe audio information).

In the data multiplexer 36 of FIG. 5, the buffer controller 12 analyzesthe information sent from the call monitor 46, determines the virtualpath identifier VPI and virtual channel identifier VCI for identifyingthe call, selects up to six channels 5 that determined the identifiersVPI and VCI, and forms a group of communication data accordingly. Thisgroup of communication data is a group which comprises communicationinformation received over different channels 5 and which complies withthe virtual path identifier VPI and virtual channel identifier VCI ofthe next stage.

When the calling subscriber starts transmitting communicationinformation (audio signal in this example), the coder-decoder 41provided for each channel 5 converts to coded information the audiosignal transmitted over the corresponding channel 5 and through theexchange 1. The conversion is carried out on the basis of the LD-CELPmethod. The coded information is accumulated in the code buffer 42 ofthe data multiplexer 36.

The buffer controller 12 monitors the amount of coded information beingaccumulated in each code buffer 42. A point is eventually reached wherethe buffer controller 12 finds that the code buffers 42 corresponding tothe six channels 5 forming the same group have each accumulated fivesets of coded information (a total of 50 bits). At that point, thebuffer controller 12 obtains the accumulated five sets of codedinformation from the buffers and stores them into a user informationpart 11 of each channel 5 in the payload 8 of the cell shown in FIG. 6.

In addition, the buffer controller 12 collects through the call monitor46 the control information on the connection status of six subscribersforming the same group (e.g., on-hook/off-hook information) as well asalarm information in connection therewith. The collected information isstored in a 10-bit control/alarm information area assigned to the sixchannels 5 in the payload 8.

Five sets of coded information (a total of 50 bits) and control/alarminformation (10 bits) are allocated to each of the six channels 5. Thesesets of coded information constitute part of the 360-bit payload 8.

In the setup of FIG. 6, each coded information area of the payload 8 isformed to a fixed length (50 bits). Alternatively, these informationareas may be formed to a variable length each. How this can be achievedwill be described later in connection with the fifth embodiment (FIG.25).

The payload 8 is assembled under control of the buffer controller 12.The payload data are then output to the ATM multiplexer 13 in accordancewith the virtual path identifier VPI and virtual channel identifier VCIdetermined commonly for those channels 5 constituting the same group.

The ATM multiplexer 13 assembles a cell by supplementing the payload 8from the upstream multiplexing part with an ATM header 7 containing thevirtual path identifier VPI and virtual channel identifier VCI. Theassembled cell is transmitted to a cross connection multiplexer 45. Thecross connection multiplexer 45 places in a queue (i.e., buffer) thecells coming from various ATM multiplexers 13. These cells are thenoutput over the ATM transmission line 3 in the order in which theyarrived.

Described below with reference to FIGS. 9 through 12 are the sequencesof control operations in effect when a call is made by the firstembodiment. In FIG. 9, the upper half shows the sequence of controloperations on the calling side of the ATM transmission apparatus 4, andthe lower half indicates the sequence of control operations on thecalled side of the ATM transmission apparatus 4.

On the calling side of the ATM transmission apparatus 4, as shown in theupper part of FIG. 9, the control signal transmitter-receiver 15 in thecall monitor 46 receives call information, i.e., a start signal and aselection signal, from a calling subscriber's terminal 2 belonging tothe same exchange 1. At that point, the control signaltransmitter-receiver 15 extracts a channel control signal from thereceived information and sends the signal to the transmission pathselector 16.

Based on the channel control signal received, the transmission pathselector 16 selects an appropriate transmission path, generates channelpath information, and sends the information to the code buffercontroller 12. In turn, the code buffer controller 12 determines thepath of an ATM cell to be generated on the basis of the channel pathinformation. With the cell path determined, the code buffer controller12 sends cell transmission path information to the ATM multiplexer 13.

Concurrently, the code buffer controller 12 reads coded information fromthe code buffer 42. If any of the channels involved is busy with a call,the code buffer controller 12 notifies the ATM multiplexer 13 with onlythe control signal such as cell transmission path information until anacknowledge signal is received from the opposite exchange. It is onlyafter the opposite exchange 1 acknowledges receipt and completion of thecall and its connection that the coded information is transmitted to theATM multiplexer 13.

FIG. 10 portrays the sequence of operations performed between the codebuffer controller 12 and the code buffer 42 in the above setup. Asdescribed, upon receipt of the channel path information from thetransmission path selector 16, the code buffer controller 12 determinesthe cell path and makes a read request to the code buffer 42 bydesignating an appropriate address thereto. The coded information isread from the code buffer 42 in response to the read request and istransferred to the code buffer controller 12. When one cell of codedinformation has been read out by the code buffer controller 12, thecontroller 12 outputs a cell generation complete notice to the ATMmultiplexer 13. The cell generation complete notice prompts the ATMmultiplexer 13 to make a read request. In turn, the code buffercontroller 12 supplies the ATM multiplexer 13 with payload informationmade of the channel control signal and of the coded information.

When the ATM multiplexer 13 prefixes the header 7 to the payloadinformation, the result is an ATM cell 10 that is transferred throughthe cross connection multiplexer 45 of FIG. 5 and on to the ATMtransmission line 3.

FIG. 11 shows the sequence of operations in effect when call informationsent from the ATM transmission apparatus 4 on the calling side isreceived as the ATM cell 10 by the ATM transmission apparatus 4 on thereceiving side. Upon receipt of the ATM cell 10, the ATM multiplexer 13sends a cell receipt acknowledge signal to the code buffer controller 12within the receiving-side ATM transmission apparatus 4. In turn, thecode buffer controller 12 makes a read request to the ATM multiplexer13. The read request prompts the ATM multiplexer 13 to read the payloadinformation (coded and control information) from the ATM cell 10. Thecode buffer controller decodes the channel path and the decoded channelpath information is sent by the code buffer controller 12 to the controlsignal transmitter-receiver 15. The channel path information received bythe control signal transmitter-receiver 15 is sent both to the callmonitor units 38 (FIG. 8) and to the transmission path selector 16.

In parallel with the above process, the code buffer controller 12 writesthe coded information to the code buffer 42. The sequence of the writeoperation is shown in FIG. 12. Specifically, upon receipt of the pathinformation from the transmission path selector 16, the code buffercontroller 12 decodes the channel path and makes a write request to thecode buffer 42. When the code buffer 42 grants permission to write, thecode buffer controller 12 writes to the code buffer 42 the codedinformation obtained from the payload 8 in the ATM cell 10. Subsequentoperations, not shown in FIG. 12, include outputting the codedinformation that came from the code buffer 42 onto the ATM transmissionline 3 and transmitting the information to the called subscriber'sterminal.

The lower half of FIG. 9 depicts the sequence of operations performed bythe ATM transmission apparatus 4 on the called side when the call isacknowledged by the called subscriber. Specifically, when thecalled-side ATM transmission apparatus 4 receives acknowledgeinformation (acknowledge signal) from the called subscriber, a callconnection signal is extracted by the control signaltransmitter-receiver 15 from the received information and is sent to thecode buffer controller 12 via the transmission path selector 16. Then inthe same sequence as shown in FIG. 10, the coded information is readfrom the code buffer 42 for cell generation. The payload information isforwarded to the ATM multiplexer 13.

The ATM multiplexer 13 prefixes the header 7 to the payload information.The payload information prefixed with the header 7 is sent to the crossconnection multiplexer 45. In turn, the cross connection multiplexer 45transmits the acknowledge information as an ATM cell 10 to the ATMtransmission apparatus 4 on the calling side.

As described, the first embodiment works roughly as follows: when thecode buffers 42 corresponding to the six calls that share a virtual pathidentifier VPI and a virtual channel identifier VCI have eachaccumulated five sets of coded information, the data multiplexer 36(buffer controller 12) in the ATM transmission apparatus 4 startsassembling one set of payload information using separately collectedcontrol and alarm information. At this point, it takes 3,125 μs (i.e.,625×5) for each of the code buffers 42 to accumulate five sets of codedinformation. That is, the coded information accumulation time with thecode buffers 42 is reduced to 5/36 of the time normally calculated withthe prior art ATM transmission apparatus 4 (22,500 μs).

Second Embodiment

The second embodiment is arranged to further multiplex ATM cells 10 intoa new ATM cell 10 through remapping in an ATM node (i.e., ATMtransmission apparatus 4), the new ATM cell being output onto the ATMtransmission line 3. Among the plurality of ATM cells 10 to bemultiplexed, the VCI value of a given ATM cell 10 is taken as the VCIvalue of the header 7 for the new ATM cell 10. The VCI values of the oldATM cells 10 are stored as channel identification information in thepayload 8 of the new ATM cell 10.

As depicted in FIG. 13, the system configuration of the ATM transmissionapparatus 4 in the second embodiment includes ATM converters (AAL's) anda path distributor 50. The path distributor 50 contains a pathidentifier 17 and a cell mapping part 18, the path identifier operatingas the call monitoring means 100. FIG. 14 is a function block diagram ofthe cell mapping part 18. The cell mapping part 18 comprises a cellmapping controller 22, a timer 20 controlled by the cell mappingcontroller 22, a mapping buffer 32, a VCI detector 21 and a cell outputpart 52.

What characterizes the second embodiment is that the signals fromsubscriber terminals 2 are converted by the ATM converters (AAL's) intoATM cells which are then remapped by the path distributor 50 into anewly multiplexed ATM cell 10 for output.

In FIG. 13, the path identifier 17 acts as a kind of selector. Whilereceiving information in the form of ATM cells 10 from the ATMconverters (AAL's), the path identifier 17 detects VPI values from thesecells. If ATM cells 10 found destined to the same path based on VPIdetection are received within a predetermined period of time, the pathidentifier 17 inputs these ATM cells into the cell mapping part 18. InFIG. 15, cells #1 and #2 have the same VPI value.

When a first ATM cell 10 (i.e., first cell #1 given after timer reset)arrives from an ATM converter (AAL), the timer 20 is activated and theVCI detector 21 is fed with a pulse signal indicating the input of thefirst ATM cell 10 (cell #1). The VCI detector 21 detects the VCI valuefrom the cell, and notifies the cell mapping controller 22 of the VCIvalue of the first ATM cell 10 (cell #1).

The cell mapping controller 22 then assembles a new ATM cell 10 (cell#A) with its VCI value taken from the first ATM cell 10 (cell #1). ThatVCI value is also stored in a channel ID part 24 of the payload 8.

When the path identifier 17 detects the arrival of an ATM cell (cell #2)having the same VPI value as that of the first cell before time is up onthe timer 20, the VCI detector 21 reads the VCI value from the header 7of the ATM cell 10 (cell #2). The cell mapping controller 22 writes theVCI value of the ATM cell (cell #2) only to the channel ID part 24 in apayload control information part 23 of the payload 8. Thereafter,whenever an ATM cell 10 is input of which the VPI value is the same asthe above, the VCI value is stored successively into the channel ID part24 of the payload 8. The successive storage of VCI values into thechannel ID part 24 continues until a time-out is reached on the timer20.

Concurrently with the storage of the VCI values, the information on theATM cells 10 (cells #1, #2, etc.) is stored consecutively into a userinformation part 11 of the payload 8.

FIG. 15 illustrates how ATM cells (cells #1, #2, etc.) are related informat to the new ATM cell (cell #A) in connection with the secondembodiment. As shown, the VPI and VCI values of the first ATM cell (cell#1) are adopted as those of the new ATM cell 10 (cell #A). The VCIinformation of the second and subsequent ATM cells is storedsuccessively into the channel ID part 24. The control information anduser information of the ATM cells 10 are placed for each channel intoareas of a fixed length each within the user information part 11 of thepayload 8 in the new ATM cell 10 (cell #A).

The channel ID part 24 accommodates, in addition to the VCI values ofthe ATM cells 10 (cells #1, #2, etc.), data length informationindicating the amount of information (significant bit count or bytelength) of each old ATM cell 10. If the control information is the sameor common to the channels 5, the information may alternatively bewritten to an appropriate address of the new ATM cell 10 (cell #A).Where one sampled data item is fixed to a data length of eight bits, aswith 64-kbps PCM audio information, the data length information may bestored as a single item or may be omitted altogether.

When a predetermined period of time has elapsed on the timer 20 (i.e.,upon time-out), the timer 20 outputs a trigger signal to the cell outputpart 52 through the cell mapping controller 22. With the trigger signaloutput, the VPI value is written to the header 7 of the new ATM cell 10(cell #A) via the cell output part 52. The ATM cell 10 (cell #A) is thenoutput onto the transmission line.

Even before the time-out of the timer 20, the cell mapping part 18outputs the trigger signal to the cell output part 52 if the userinformation part 11 of the ATM cell 10 (cell #A) has been filled tocapacity with information. This prompts the output of the ATM cell 10(cell #A). At this point, the timer 20 is reset regardless of thetime-out that may or may not be reached on the timer.

In the receiving side ATM node, the old VCI values of the old ATM cells(cells #1, #2, etc.) are extracted from the channel ID part 24 in thepayload 8 of the new ATM cell 10 (cell #A). At the same time, the datalength information is read out to determine the allocation of theinformation for the respective old cells. The operations combine toreassemble the old ATM cells 10 (cells #1, #2, etc.).

Although the above setup involves storing the VCI value of the first ATMcell (cell #1) in the channel ID part 24 of the payload 8, the channelID part 24 may alternatively accommodate the VCI values of the secondand subsequent ATM cells 10 (from cell #2 on). In the latter case, theVCI value ill the header 7 of the ATM cell 10 (cell #A) that has arrivedmay be used unchanged as the first user information on the receivingside.

Although the above setup uses the VCI value of the first ATM cell 10(cell #1) as the VCI value of the new ATM cell 10 (cell #A), analternative arrangement may be employed. Specifically, the maximum orminimum VCI value of the old ATM cells 10 (cells #1, #2, etc.) may bedetected by the VCI detector 21. Then the cell mapping part 18 may writethe maximum or minimum VCI value to the header 7 of the new ATM cell 10(cell #A). In this case, the writing of the VCI value to the header 7 ofthe new ATM cell 10 (cell #A) is accomplished after mapping.

As described, the second embodiment assembles old ATM cells 10 (#1, #2,etc.) regardless of their many dummy patterns (see FIG. 15) into a newATM cell (#A) with no dummy pattern. In this manner, the payload 8 ofthe new ATM cell 10 is utilized efficiently. Because the assembly of thenew ATM cell 10 is monitored by the timer 20, there is no delay in theoutput of that cell.

FIG. 16 depicts the format of a channel ID part in a new ATM cell (#A)produced by a variation of the second embodiment. One way to apportionVPI and VCI values of ATM cells in the channel ID format is to setlow-order n bits as per the number of paths or channels needed by theuser while the high-order bits are fixed (e.g., all bits fixed to zero).In the example of FIG. 16, the channel ID part 24 of the new ATM cell 10(#A) accommodates only the low-order n bits and VCI significant bitcount of the VCI values from the old ATM cells 10 (#1, #2, etc.).

According to the preceding method, three bits are enough when it comesto expressing, say, five channels for use by a single path (VPI). Evenif the use of "000" is prohibited by the user, a three-bit formatprovides expressions of up to seven channels (001-111).

Where the above method is employed, the cell mapping part 22 takes thesignificant bit count n (n=7 in the above example) of the VCI valuesfrom the input ATM cells 10 (#1, #2, etc.) and stores the count into asignificant bit count storage part of the channel ID part 24 in thepayload 8. Following the bit count storage part, the cell mapping part22 stores consecutively the low-order n bits of the VCI values from theinput ATM cells 10.

The value n may be determined in one of two ways: either it is set whenentered initially through the network, or it is determined as neededbased on the information obtained from the VCI detector 21. In any case,the format of FIG. 16 allows the channel ID part 24 to be usedefficiently so that an extensive user information part 11 will besecured in the payload 8.

Third Embodiment

In the third embodiment, an ATM node (i.e., ATM transmission apparatus4) further multiplexes the information in the form of ATM cells 10 intoa new ATM cell 10 through remapping, and outputs the new ATM cell toanother ATM node. Among the plurality of ATM cells 10 to be multiplexed,the VCI value of a given ATM cell 10 is taken as the VCI value of theheader 7 for the new ATM cell 10. The VCI values of the old ATM cells 10are converted to channel numbers through a management table 25 forstorage into the channel ID part 24 of the new ATM cell 10..

FIG. 17 portrays the system configuration of the third embodiment. InFIG. 17, the cell mapping controller 22 is basically the same incomposition as that of the second embodiment except for the managementtable 25 shown in the figure. The other components that are functionallyidentical to those described in connection with the second embodimentare designated by the same reference numerals, and any repetitivedescription thereof is omitted. As depicted in FIG. 17, the managementtable 25 is made of conversion tables each converting the VCI numbersunder a given VPI into channel numbers.

When notified of the VCI values of the old ATM cells 10 (#1, #2, etc.)by the VCI detector 21, the cell mapping controller 22 references theconversion table of the applicable VPI in the VCI management table 25,and reads the corresponding channel numbers therefrom. The channelnumbers thus read out are written consecutively, together with datalength information, to the channel ID part 24 of the new ATM cell 10(#A).

FIG. 18 illustrates the format of the channel ID part 24 in a new ATMcell produced by the third embodiment. As with the second embodiment, ifthe data length is the same throughout the payload user information part11 of this format, only one data length may be stored, or the storage ofdata lengths may be omitted altogether.

Fourth Embodiment

In the fourth embodiment, an ATM node (i.e., ATM transmission apparatus4) further multiplexes the information in the form of ATM cells 10 intoa new ATM cell 10 through remapping, and outputs the new ATM cell toanother ATM node. What characterizes the fourth embodiment is that arepresentative VCI indicating a plurality of multiplexed cells is storedas the VCI value of the new ATM cell 10.

FIG. 19 depicts the system configuration of the fourth embodiment whichincludes a representative VCI prefixing part 53. The other componentsthat are functionally identical to those described in connection withthe second embodiment are designated by the same reference numerals, andany repetitive description thereof is omitted.

With the fourth embodiment, the cell mapping controller 22 sends atrigger signal to the representative VCI prefixing part 53 immediatelyafter reset or time-out of the timer 20 or when the user informationpart 11 of the payload 8 has been filled with information. This causesthe representative VCI value to be written to the header 7 of the newATM cell 10 (#A). The representative VCI stands for a plurality of cellsbeing multiplexed and is preferably reserved as a special number. FIG.20 shows how old ATM cells 10 (#1, #2, etc.) compare in format with thenew ATM cell 10 (#A) in connection with the fourth embodiment.

Upon receipt of the multiplexed ATM cell 10 (#A) prefixed with therepresentative VCI, the ATM node on the receiving side disassembles theATM cell 10 (#A) into the original plurality of ATM cells 10 (#1, #2,etc.). The disassembled ATM cells 10 are transferred to the terminalscorresponding thereto. If an ATM cell 10 (#B) has no representative VCIprefixed thereto, the cell is transferred intact to the correspondingterminal or ATM transmission apparatus 4.

The prefixing of the representative VCI may be implemented by combiningthe methods of the second and third embodiments.

Fifth Embodiment

The fifth embodiment involves dividing into variable lengths a pluralityof items of information generated by terminals (i.e., terminalequipment; TE) in an in-house setup and multiplexing these items in thepayload 8 of an ATM cell 10.

FIG. 21 sketches the overall system configuration of the fifthembodiment. In the in-house setup of FIG. 21, terminals 31 (TE)connected to in-house bus means 28 coming from network transit switchingequipment 26 are illustratively multimedia terminals. Each of theseterminals incorporates a pair of interface parts 30 (See FIG. 22) thattransmit and receive image information, audio information, text data andother data in the form of ATM cells 10. FIG. 22 illustrates an interfacepart 30 in more detail. As depicted, the interface part 30 comprises anATM multiplexer 13, a buffer controller 12 and a buffer 54. In eachterminal (TE), one interface part 30 is located on the upward-bound busside and the other interface part 30 on the downward-bound bus side.

FIG. 23 is a function block diagram showing how the buffer controller 12and the ATM multiplexer 13 operate on the transmitting side of the fifthembodiment, and FIG. 24 is a function block diagram depicting how thesame components operate on the receiving side.

What takes place on the transmitting side of the fifth embodiment inFIG. 23 is as follows: data items (A, B, C, . . . , N) from terminalsare first written to the buffer 54. When a buffer input counter 2302 hascounted the data items up to a predetermined value, the counter notifiesan input transmission rate calculation part 2303 that the predeterminedcount value is reached. Based on that input count value, the inputtransmission rate calculation part 2303 calculates the transmission rateof the input data and notifies a payload assembly ratio calculation part2305 of that rate. At the same time, a desired transmission rate requestprocessing part 2304 receives desired transmission rate requests fromthe terminals (TE) and notifies the payload assembly ratio calculationpart 2305 of these requests.

Based on the received information and on the data from a bus monitoringand processing part 2312, the payload assembly ratio calculation part2305 determines how the different data items are to be allocated in thepayload 8. The data allocation thus determined is sent to a sub-headerassembly part 2309 and to a read order and amount controller 2306 of thepayload control information part 23.

In turn, the read order and amount controller 2306 activates individualinput buffer reading part 2307 which reads necessary amounts of datafrom the buffer 54 in a predetermined order. The read-out data arehanded over to a payload data assembly part 2308 of the ATM multiplexer13.

After the sub-header assembly part 2309 prefixes the payload controlinformation part 23 as a sub-header 7 to the payload 8, an ATM headerprefixing part 2310 prefixes the other items of the header 7 (e.g., VPI,VCI) to the ATM cell 10. The completed ATM cell 10 is then sent to atransmission buffer 2311 (first-in first-out memory) in the ATMmultiplexer 13. From the buffer 2311, the ATM cell 10 is output onto thein-house bus means 28.

What takes place on the receiving side of the fifth embodiment in FIG.24 is as follows: when an ATM cell 10 is received through the in-housebus means 28 (FIGS. 21 and 22), cell receipt information is sent from anATM header identification part 2413 to a bus monitoring and processingpart 2412 within the ATM multiplexer 13. This causes necessaryprocessing to take place according to the protocol (e.g., DQDB protocol)of the in-house bus means 28.

The ATM cell thus received is accumulated in a reception buffer 2414(first-in first-out memory) in the ATM multiplexer 13. Thereafter, theATM cell is sent both to a sub-header removal part 2416 and to asub-header analysis part 2415, the latter analyzing the sub-header 7held in the payload control information part 23. In accordance with theresult of the analysis on the sub-header 7, the payload controlinformation part 23 is removed and the user information part 11 of thepayload 8 is disassembled by a payload data disassembly part 2417.Following disassembly, image information, audio information, text dataand other data are transferred to individual data transmission bufferwriting parts 2419 via individual data buffers 2418 (first-in first-outmemory). These kinds of information are read from the buffers accordingto the transmission rate determined by a desired transmission raterequest processing part 2421.

What characterizes the fifth embodiment is that, as discussed withreference to FIG. 23, the relative ratio at which to assemble differentdata into the payload 8 is varied (by the payload assembly ratiocalculation part 2305) in accordance with the desired transmission ratesrequested and with the actually input transmission rate. While the firstthrough the fourth embodiment allocate data in a fixed length formatwithin the payload 8 upon multiplexing of information in the ATM cell10, the fifth embodiment allocates data in a variable length formatwithin the payload 8.

FIG. 25 is a conceptual view illustrating how ATM cells are multiplexedby the fifth embodiment. In FIG. 25, transmitted information composed offour data types (data A through data D in the upper part of the figure)is shown multiplexed in variable lengths (in the lower part of thefigure) within the payload 8 of an ATM cell 10. These four kinds of data(data A-D) may be data for a different channel each (e.g., data Arepresenting image, data B sound, data C text data). The fifthembodiment is particularly effective when used with an in-house setupwherein multimedia terminals connected to an in-house LAN are oftenrequired to transmit and receive information of different channels insynchronism.

Generally, the ATM cell 10 comprises the ATM header 7, payload controlinformation part 23 and payload user information part 11. The ratio ofassembling each of different types of information into the payload userinformation part 11 is calculated by the payload assembly ratiocalculation part 2305. The ratio is determined after consideration ofsuch factors as whether or not the information to be transmitted needsto be processed at high speed and whether or not the information is tobe handled on a burst basis.

FIG. 26 shows typical contents of payload control information parts inATM cells (i.e., lower half of what is depicted in FIG. 25) inconnection with the fifth embodiment, and FIG. 28 gives a detailedformat of one of such ATM cells. As illustrated in FIG. 28, the payloadcontrol information part 23 contains a DB header (first control area 34)and a DC header (second control area 35). The DB header comprisesidentifiers each indicating the beginning, an intermediate portion orthe end of the information in question. The DC header includesidentifiers indicating the data length of each item of information heldin this ATM cell 10.

Take, for example, the first ATM cell 10 (cell 1) shown in the lowerhalf of FIG. 25. This ATM cell contains the beginning of each of data Athrough data C, while data D is not stored. Thus the DB header containsan identifier (e.g., "01") indicating the beginning of each of data Athrough data C, and includes another identifier (e.g., "00") indicatingthe absence of data D (see FIG. 29, to be discussed later). The DCheader stores the data length of each of the different data (A1, B1, C1;see FIG. 30, to be discussed later).

On the receiving side, the DB and DC headers are read out of the payloadcontrol information part 23. The information contained in the headersallows the receiving-side ATM transmission apparatus to recognize whatkinds of information are held and how they are allocated in the payloaduser information part 11 of the ATM cell 10 in question. With thenecessary information thus revealed, the original data A through D arerestored precisely. FIG. 27 describes how the ATM cells multiplexed bythe fifth embodiment as shown in the lower half of FIG. 25 are restoredback to the original data (data A through D).

In the ATM cell format shown in FIG. 28, what characterizes the fifthembodiment is that, as mentioned above, the payload user informationpart 11 is headed by the payload control information part 23 whichcomprises the first control area 34 and second control area 35. Thefirst and the second control areas 34 and 35 accommodate the DB headerand DC header, respectively, as identifiers. The DB header may store upto four identifiers, two bits in length each. The meanings of theseidentifiers, (DCF's) are listed in FIG. 29.

In FIG. 29, a bit string "00" held in a DCF means that no data is storedin the corresponding payload user information part 11 a bit string "01"means that the beginning of transmitted data is stored a bit string "10"means that an intermediate portion of the transmitted data is stored anda bit string "11" means that the end of the transmitted data is stored.

The DC header may contain up to four pairs of identifiers, each pairindicating a data length (DL) and a data sequence (DSN, or data sequencenumber). The DL identifier denotes the length of the corresponding dataaccommodated in the payload user information part 11 (to be describedbelow), and the DSN identifier designates the data sequence number ofthe applicable data as counted from the first data.

The payload user information part 11 ranges from the eleventh octet tothe fifty-second octet. Actual data are allocated in this part accordingto the ratio determined for the respective data. FIG. 31 shows theformat of an ATM cell that contains actual data in connection with thefifth embodiment.

As described and according to the fifth embodiment, numerous kinds ofdata are multiplexed in each ATM cell 10 in which the payload 8 isapportioned in variable lengths. This feature boosts the efficiency ofdata transmission and makes effective use of the available trafficcapacity thanks to the high concentration of transmitted data.

Because there is no need to classify data types on a network 27 (in FIG.21), the structure of the network can be simplified.

With no need to change transmission and reception protocols on anyterminal (TE) for each different type of data to be transmitted in anin-house setup, the terminal may be made smaller in size and simpler instructure than before.

Since it is not necessary to repeat call settings for each set of datato be transmitted, the call setting procedure becomes more efficient. Asa result, transmission costs are reduced.

The ease of keeping synchronism between a plurality of kinds of data forsimultaneous transmission contributes to preventing the voice or imagedrop-out during multimedia information transmission.

As many apparently different embodiments of this invention may be madewithout departing from the spirit and scope thereof, it is to beunderstood that the invention is not limited to the specific embodimentsthereof except as defined in the appended claims.

What is claimed is:
 1. A cell multiplexing apparatus for receivingcommunication information over a minimum of two channels and fortransmitting the communication information to a transmission line, saidcell multiplexing apparatus comprising:call monitoring means forobtaining call setting information from said communication information,indicative of monitor control information for each channel; and at leastone multiplexing means, each of said at least one multiplexing means formultiplexing said communication information received over said minimumof two channels into a single cell of a fixed length and comprising aheader and a payload, in accordance with said call setting informationobtained by said call monitoring means, and transmitting said singlecell to the transmission line, wherein each of said at least onemultiplexing means comprises:coding-decoding means for coding intodigital format the communication information received from subscriberterminals via said channels, a minimum of two code buffer means foraccumulating said communication information from respective saidchannels in said digital format, buffer control means for assemblingsaid payload of said respective single cell by monitoring each of saidcode buffer means, and asynchronous transfer mode multiplexing means forprefixing a header to said respective single cell of which said payloadis assembled by said buffer control means; wherein said buffer controlmeans reads a fixed quantity of said communication information from saidminimum of two code buffer means so as to assemble said payload of saidrespective single cell each time said buffer control means detects saidfixed quantity of said communication information stored into each ofsaid code buffer means.
 2. The cell multiplexing apparatus according toclaim 1, wherein said at least one multiplexing means comprises aminimum of two multiplexing means, each of said minimum of twomultiplexing means including said coding-decoding means, said minimum oftwo code buffer means, said buffer control means and said asynchronoustransfer mode multiplexing means, said cell multiplexing apparatusfurther comprising:cross connection multiplexing means for connectingsaid minimum of two multiplexing means, to alternately enabletransmission of said single cells from respective multiplexing means,based upon order of receipt of said single cells by said crossconnection multiplexing means.
 3. The cell multiplexing apparatusaccording to claim 1, wherein said call monitoring means comprises:aplurality of call monitors, each call monitor connected to a distinctplurality of the channels, each call monitor monitoring the status ofcalls on corresponding channels connected to said each call monitor; andeach of said plurality of call monitors further comprising:controlsignal transmitting-receiving means for recognizing channel controlsignals received over respective ones of the distinct plurality ofchannels connected thereto; and transmission path selecting means forextracting channel path information from each of said channel controlsignals received and for supplying a corresponding one of said buffercontrol means with said channel path information; and wherein saidcorresponding one of said buffer control means, upon receipt of saidchannel path information from said transmission path selecting means,determines the path of said respective single cell.
 4. A cellmultiplexing apparatus for receiving communication information over aminimum of two channels and for transmitting the communicationinformation to a transmission line, said cell multiplexing apparatuscomprising:call monitoring means for obtaining call setting informationfrom said communication information, indicative of monitor controlinformation for each channel; and at least one multiplexing means, eachof said at least one multiplexing means for multiplexing saidcommunication information received over said minimum of two channelsinto a single cell of a fixed length and comprising a header and apayload, in accordance with said call setting information obtained bysaid call monitoring means, and transmitting said single cell to thetransmission line; wherein said call monitoring means comprises pathidentifying means for receiving said communication information stored ina plurality of cells smaller than each single cell and for monitoringrespective headers of the received cells, capturing only those receivedcells having an identical virtual path identifier; and wherein each ofsaid multiplexing means comprises cell mapping means for multiplexing aminimum of two of said plurality of cells having the same virtual pathidentifier into one of said single cells.
 5. The cell multiplexingapparatus according to claim 4, wherein said cell mapping meanscomprises:timer means for counting the time required to capture thereceived cells having the same virtual path identifier, to generatetiming information; virtual channel identifier detecting means fordetecting virtual channel identifiers from the captured cells; and cellmapping control means for generating a header and a payload of said oneof said single cells based on the timing information coming from saidtimer means and said virtual channel identifiers identified by saidvirtual channel identifier detecting means; and wherein said cellmapping control means takes the virtual channel identifier held in theheader of the first cell captured from the received cells having thesame virtual path identifier, stores said virtual channel identifier inthe header of said one of said single cells, and fills a channelidentifier part of a payload control information part in the payload ofsaid one of said single cells with the virtual channel identifiers ofthe second and subsequent cells captured.
 6. The cell multiplexingapparatus according to claim 5,wherein said cell mapping control meanstakes a representative virtual channel identifier indicating saidplurality of cells, uses said representative virtual channel identifieras the channel identifier of said one of said single cells, and storesthe virtual channel identifiers of the cells captured by said pathidentifying means into said channel identifier part of said payloadcontrol information part in the payload of said one of said singlecells.
 7. The cell multiplexing apparatus according to claim 4, whereinsaid cell mapping means comprises:timer means for counting the timerequired to capture the received cells having the same virtual pathidentifier, to generate timing information; virtual channel identifierdetecting means for detecting virtual channel identifiers from thecaptured cells; cell mapping control means for generating a header and apayload of said one of said single cells based on the timing informationcoming from said timer means and said virtual channel identifiersidentified by said virtual channel identifier detecting means, said cellmapping control means taking one of a maximum virtual channel identifierand a minimum virtual channel identifier associated with one cellcaptured from among the received cells having the same virtual pathidentifier, stores the virtual channel identifier thus taken into theheader of said one of said single cells, and fills said channelidentifier part of said payload control information part in the payloadof said one of said single cells with the virtual channel identifiers ofthe remaining cells captured other than the cell having the takenvirtual channel identifier.
 8. The cell multiplexing apparatus accordingto claim 7, wherein said cell mapping means takes low-order bits aloneof said virtual channel identifiers associated with said remaining cellscaptured, and stores successively said low-order bits into said channelidentifier part of said payload control information part in the payloadof said one of said single cells.
 9. The cell multiplexing apparatusaccording to claim 7, wherein:said cell mapping means further comprisesa management table containing channel numbers corresponding to virtualchannel numbers under each virtual path identifier and said cell mappingmeans converts the virtual channel identifiers of said remaining cellscaptured to the corresponding channel numbers by referring to saidmanagement table, and stores said corresponding channel numbers intosaid channel identifier part of said payload control information part inthe payload of said one of said single cells.
 10. A cell multiplexingapparatus for transmitting information in cells, each cell made of aheader and a payload in an in-house communication line setup, saidapparatus comprising:in-house bus means; in-house terminal meansincluding a plurality of information sources connected to said in-housebus means via interface means, for interfacing with said in-house busmeans, said in-house bus means transmitting said cells between each ofsaid in-house terminal means; said interface means comprising:buffermeans for accumulating a plurality of transmission information from eachpiece of said information from each information source; buffer controlmeans for multiplexing the information accumulated in said buffer meansinto the payload of a respective one of the cells; and asynchronoustransfer mode multiplexing means for setting said header to indicatesaid payload being multiplexed with a plurality of said information. 11.The cell multiplexing apparatus according to claim 10, wherein saidbuffer control means comprises payload assembly ratio calculating meansfor receiving from said in-house terminal means requests for desiredrates at which to transmit information, for calculating the transmissionrate of information input to said buffer means, and for calculating theratio at which to apportion into said payload at least two items of theinformation to be transmitted.
 12. The cell multiplexing apparatusaccording to claim 10, wherein the payload of each of said cells isdivided into a payload control information part and a payload userinformation part;said payload control information part having a firstcontrol area and a second control area, said first control area storingidentifiers each indicating to which part of the entire informationtransmitted the corresponding portion of information held in saidpayload user information part belongs, said second control area storingidentifiers each indicating the length of the corresponding portion ofinformation held in said payload user information part; and said payloaduser information part accommodating at least two variable-lengthportions of information corresponding to the identifiers stored in saidsecond control area of said payload control information part.
 13. A cellmultiplexing apparatus for receiving communication information overgroups of channels, each group of channels comprising at least twochannels, and for transmitting the communication information to atransmission line, said cell multiplexing means comprising:a pluralityof call monitoring means for obtaining call setting information fromsaid communication information received over respective groups ofchannels, said call setting information indicative of monitor controlinformation for each channel; and a plurality of data multiplexing meansfor multiplexing said communication information received over respectivegroups of said channels into respective single cells, each single cellbeing of a fixed length and comprising a head and a payload, inaccordance with said call setting information obtained by said callmonitoring means; and cross connection multiplexing means for receivingsaid single cells from said plurality of data multiplexing means andalternately enabling transmission of said single cells to thetransmission line.
 14. The cell multiplexing apparatus as claimed inclaim 13, wherein each of said data multiplexing means comprises:aplurality of coding-decoding means for coding the communicationinformation from said respective groups of channels into digital data; aplurality of code buffer means for accumulating said digital data fromrespective ones of said plurality of coding-decoding means; buffercontrol means for assembling said payload of said respective singlecell, by monitoring each of said plurality of code buffer means, saidbuffer control means reading a fixed quantity of said communicationinformation from each of said plurality of code buffer means, toassemble said payload of said respective single cell each time saidbuffer control means detects said fixed quantity of communicationinformation stored in each of said code buffer means; and asynchronoustransfer mode multiplexing means for prefixing a header to saidrespective single cell.
 15. A cell multiplexing apparatus fortransmitting information in cells, each cell made of a header and apayload in an in-house communication line setup, said apparatuscomprising:in-house bus; in-house terminal means including a pluralityof information sources connected to said in-house bus means viainterface means, for interfacing with said in-house bus means, saidin-housing bus means transmitting said cells between each of saidin-house terminal means; said interface means comprising:buffer meansfor accumulating communication data of a plurality of information typesfrom the corresponding plurality of information sources; transmissionrate determining means for determining desired transmission rates foreach of the plurality of information types; buffer control means fordetermining transmission rates of the communication data for each of theplurality of information types accumulated in said buffer means anddetermining the communication data of the plurality of information typesto be allocated into the payload of a respective one of the cells, basedupon said desired transmission rates and said communication data; andasynchronous transfer mode multiplexing means for multiplexing thecommunication data into the payload of said respective cell and addingsaid header to said payload.